Bike Suspension Glossary: Fork, Shock, Sag and Rebound

A fork with a spring and damper that absorbs impacts. Typical travel: 100-120 mm for XC, 130-150 for trail, 160-180 for enduro and 200 mm for downhill.

See also: travel, stanchions, lowers, sag

The spring and damper unit of the rear suspension. It's identified by its eye-to-eye length and stroke, for example 210 × 55 mm, and by its mounting type.

See also: eye-to-eye length, shock stroke, rocker link

The most the suspension can compress, measured at the wheel, in millimeters. More travel soaks up bigger hits, at the cost of more weight and less pedaling efficiency.

See also: sag, shock stroke, suspension fork

How far the shock itself compresses, much less than the wheel travel. With 55 mm of stroke and 140 mm of travel, the average leverage ratio is 2.55.

See also: eye-to-eye length, leverage ratio, travel

The length of the shock between the centers of its two mounts. Together with stroke, it decides which shocks fit a frame: 210 × 55, 230 × 65…

See also: rear shock, shock stroke

How much of the travel the suspension uses under your weight alone, in riding position. It's usually set at 15-20% on XC forks, 25-30% on trail bikes and up to 30-35% at the rear on enduro bikes.

See also: air spring, travel, rebound

How fast the suspension extends after compressing. Too fast and the bike bucks; too slow and it packs down after several hits in a row. The adjuster is usually red.

See also: compression, sag

The suspension's resistance to compressing. It's adjusted with the blue dial and is often split into low-speed (pedaling, braking, cornering) and high-speed (sharp hits, jumps).

See also: rebound, lockout, progression

A setting that almost fully firms up the suspension for climbing or riding on pavement without it bobbing when you pedal. It can be on the fork itself or on a handlebar remote.

See also: compression, anti-squat

A spring made of a pressurized air chamber. It's light and you set it for your weight with a shock pump, in psi, following the manufacturer's chart.

See also: negative air chamber, volume spacers (tokens), coil spring

A steel or titanium spring. It's very supple over small bumps and doesn't heat up, but it's heavier, and to change firmness you have to swap the spring, which is sold by its rate in pounds per inch (lbs/in).

See also: air spring, rear shock

The chamber of an air spring that pushes in the opposite direction to the main one. It helps the suspension start moving on small bumps; on most models it equalizes on its own when you compress it a little.

See also: air spring, sag

Plastic pieces that reduce the volume of the air chamber. They make the suspension more progressive at the end of the travel, so you bottom out less without changing sag.

See also: progression, bottom-out, air spring

How much the suspension firms up as it compresses. A progressive suspension is soft at the start and firm at the end, which helps you avoid bottoming out on big hits.

See also: volume spacers (tokens), leverage ratio, bottom-out

The relationship between how far the rear wheel moves and how far the shock compresses at each point in the travel. Its curve defines a suspension's character: if it falls through the travel, it's progressive.

See also: shock stroke, progression, rocker link

The rear suspension's ability to resist the compression caused by pedaling. With values near 100% at sag, the bike barely bobs when you pedal.

See also: lockout, rocker link

Using all the travel and hitting the end of it hard. Bottoming out now and then on the biggest jump of the ride is normal; if it happens often, you need more pressure or more progression.

See also: volume spacers (tokens), progression, sag

The polished upper tubes of a suspension fork that slide in and out of the lowers. Their diameter (32, 34, 36, 38 mm…) tells you stiffness and intended use; a scratch on them eventually causes oil leaks.

See also: lowers, seals (wipers), fork crown

The lower part of the fork, one piece with the arch, that the stanchions slide into. Inside is oil that lubricates the bushings and gets changed in a basic service.

See also: stanchions, seals (wipers), fork arch, suspension service

Rubber seals at the top of the lowers that wipe the stanchions and keep dirt out and oil in. If you see a ring of oil on the stanchion after a ride, it's time to check them.

See also: stanchions, lowers, suspension service

The part that joins the two stanchions to the steerer tube. Downhill forks have two crowns, one below and one above the head tube.

See also: stanchions, steerer tube

The bridge that joins the two lowers in front of or behind the wheel and gives the fork side-to-side stiffness. It sets the maximum tire width and diameter that will fit.

See also: lowers, tire

A pivoting part that connects the rear triangle to the shock on many suspension designs. Its shape is how the manufacturer sets leverage ratio and progression.

See also: leverage ratio, rear shock, bearing

A bike with front and rear suspension. It has more traction and comfort on rough terrain, but weighs a bit more and needs more maintenance than an equivalent hardtail.

See also: hardtail, rear shock, rocker link

A mountain bike with a suspension fork and no rear suspension. It's lighter, cheaper and simpler to maintain, and still very common in XC and on entry-level bikes.

See also: full suspension, suspension fork

A seatpost with a spring or elastomer that absorbs vibration, with about 20 to 50 mm of travel. It's used on gravel, city and touring bikes.

See also: seatpost, dropper post

Regular maintenance of the fork and shock. A basic service cleans the lowers and replaces oil and seals; a full service includes the damper cartridge. RockShox, for example, recommends the basic one every 50 hours of riding and the full one every 200.

See also: seals (wipers), lowers